Fix NPE when traversing map

pom.xml

@@ -5,7 +5,7 @@
 
 	<groupId>org.springframework.data</groupId>
 	<artifactId>spring-data-mongodb-parent</artifactId>
-	<version>4.3.0-SNAPSHOT</version>
+	<version>4.3.x-4567-SNAPSHOT</version>
 	<packaging>pom</packaging>
 
 	<name>Spring Data MongoDB</name>

spring-data-mongodb-benchmarks/pom.xml

@@ -7,7 +7,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>4.3.0-SNAPSHOT</version>
+		<version>4.3.x-4567-SNAPSHOT</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 

spring-data-mongodb-distribution/pom.xml

@@ -15,7 +15,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>4.3.0-SNAPSHOT</version>
+		<version>4.3.x-4567-SNAPSHOT</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 

spring-data-mongodb/pom.xml

@@ -13,7 +13,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>4.3.0-SNAPSHOT</version>
+		<version>4.3.x-4567-SNAPSHOT</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/QueryMapper.java

@@ -617,15 +617,20 @@ protected Object convertSimpleOrDocument(Object source, @Nullable MongoPersisten
 
 		if (source instanceof Map<?,?> sourceMap) {
 
-			return sourceMap.entrySet().stream().collect(Collectors.toMap(
-					entry -> ObjectUtils.nullSafeToString(converter.convertToMongoType(entry.getKey())),
-					entry -> {
-						if (entry.getValue() instanceof Document document) {
-							return getMappedObject(document, entity);
-						}
-						return delegateConvertToMongoType(entry.getValue(), entity);
-					}
-			));
+			Map<String, Object> map = new LinkedHashMap<>(sourceMap.size(), 1F);
+
+			sourceMap.entrySet().forEach(it -> {
+
+				String key = ObjectUtils.nullSafeToString(converter.convertToMongoType(it.getKey()));
+
+				if (it.getValue() instanceof Document document) {
+					map.put(key, getMappedObject(document, entity));
+				} else {
+					map.put(key, delegateConvertToMongoType(it.getValue(), entity));
+				}
+			});
+
+			return map;
 		}
 
 		return delegateConvertToMongoType(source, entity);

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/convert/QueryMapperUnitTests.java

@@ -28,6 +28,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import java.util.TreeMap;
 
 import org.bson.conversions.Bson;
 import org.bson.types.Code;
@@ -1517,6 +1518,20 @@ void usesKeyNameWithDotsIfFieldNameTypeIsKey() {
 		assertThat(mappedObject).isEqualTo("{ 'field.name.with.dots' : 'A' }");
 	}
 
+	@Test // GH-4577
+	void mappingShouldRetainMapKeyOrder() {
+
+		TreeMap<String, String> sourceMap = new TreeMap<>(Map.of("test1", "123", "test2", "456"));
+
+		org.bson.Document target = mapper.getMappedObject(query(where("simpleMap").is(sourceMap)).getQueryObject(),
+				context.getPersistentEntity(WithSimpleMap.class));
+		assertThat(target.get("simpleMap", Map.class)).containsExactlyEntriesOf(sourceMap);
+	}
+
+	class WithSimpleMap {
+		Map<String, String> simpleMap;
+	}
+
 	class WithDeepArrayNesting {
 
 		List<WithNestedArray> level0;

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/convert/UpdateMapperUnitTests.java

@@ -762,6 +762,18 @@ void mappingShouldNotContainTypeInformationWhenValueTypeOfMapMatchesDeclaration(
 		assertThat(mappedUpdate).doesNotContainKey("$set.concreteMap.jasnah._class");
 	}
 
+	@Test // GH-4567
+	void updateShouldAllowNullValuesInMap() {
+
+		Map<Object, NestedDocument> map = Collections.singletonMap("jasnah", new NestedDocument("kholin"));
+
+		Update update = new Update().set("concreteMap", Collections.singletonMap("jasnah", null));
+		Document mappedUpdate = mapper.getMappedObject(update.getUpdateObject(),
+				context.getPersistentEntity(EntityWithObjectMap.class));
+
+		assertThat(mappedUpdate).isEqualTo(new Document("$set", new Document("concreteMap", Collections.singletonMap("jasnah", null))));
+	}
+
 	@Test // DATAMONGO-1250
 	@SuppressWarnings("unchecked")
 	void mapsUpdateWithBothReadingAndWritingConverterRegistered() {